Let us explain above statement with the help of example where mobile is kept on the table is resting at its position
Now what do you think about this mobile:-
(a)is it at rest or
(b) is it moving i.e., changing its position with the passage of time.
Now we have stated previously that:
Motion and rest are relative terms
☛ So for a person seeing mobile from earth it is at rest
☛ Now consider a hypothetical scenario where we station our self on moon.
☛ Now from there earth seems to change its position with time (earth is rotating on its axis) and so mobile along with the table is
changing its position.
☛ So, it is moving
for a person tracking it from moon.